1. Field of the Invention
The invention relates to a switching arrangement for a high-power RF GTO comprising a latching-type semiconductor component having an anode, a cathode and a gate and means for generating a gate current I.sub.G at the gate for turning off the semiconductor component.
2. Discussion of Background
Today, about 190 GTO types from well over 10 semiconductor manufacturers are available on the market. Their application is mainly divided into three important fields, namely traction (for example locomotives), UPS (uninterruptible power system) and industrial drive systems. This wide distribution has occurred in spite of the fact that the GTO has some problems for the user, for example with respect to circuit engineering. An improvement of the GTO with respect to its protective circuit therefore has enormous economic significance.
The user is confronted, in particular, by the following problems in connection with the GTO:
complexity in the drive system; PA1 turn-off failures; PA1 maintenance of the spike voltage; PA1 switching losses in the GTO and in the protective circuit; PA1 cooling.
Gate turn-off thyristors (GTOs) have hitherto had to be operated with protective networks (snubbers) of considerable complexity. Apart from the additional weight, increased volume and considerable losses, this also entails, in particular, additional development and production costs. The development of control software is also much more expensive due to the complicated mode of operation determined by the snubbers. The aim is therefore to reduce the size of the snubbers (smaller inductances and smaller capacitances) and to simplify them. An important role is played by, in particular, the stray inductance and the snubber diode. A considerable design effort must be made to reduce overvoltages. Recently, quite special diodes have also been developed for these applications.
It has been recognized that the reason for requiring snubbers lies in the non-homogeneous turning-on and off characteristics of the GTOs: this fact has been emphasized time and again in long studies involving infrared, thermal and induction measurements. Efforts have therefore been directed towards the production of the most homogeneous components possible (particularly with respect to doping). In spite of significant improvements in the doping homogeneity, however, it has not been possible to simplify or reduce the size of the snubbers to any significant extent.
The desired aim of users and manufacturers is the RF GTO. This should be distinguished by, among other things, a greatly reduced protective circuit complexity, by low drive power and few turn-off failures. Until now, however, it has not been known how such a component should look and how it should be operated. Ignorance of the true causes of the turn-off failures in the GTO is a great impediment.